The present invention generally relates to a very low emission hybrid electric vehicle incorporating an integrated propulsion system. More particularly, the present invention relates to a hydrogen powered internal combustion engine for use in the hybrid vehicle. The hydrogen powered internal combustion hydrogen engine operates without a throttle and utilizes a cylinder deactivation strategy to reduce power under idle and light load conditions.
As the world""s population expands and its economy increases, the atmospheric concentrations of carbon dioxide are warming the earth causing climate change. However, the global energy system is moving steadily away from the carbon-rich fuels whose combustion produces the harmful gas. Experts say atmospheric levels of carbon dioxide may be double that of the pre-industrial era by the end of the next century, but they also say the levels would be much higher except for a trend toward lower-carbon fuels that has been going on for more than 100 years. Furthermore, fossil fuels cause pollution and are a causative factor in the strategic military struggles between nations.
For nearly a century and a half, fuels with high amounts of carbon have progressively been replaced by those containing smaller and smaller amounts of carbon. First wood, which is high in carbon, was eclipsed in the late 19th century by coal, which contains less carbon. Then oil, with a lower carbon content still, dethroned xe2x80x9cKing Coalxe2x80x9d in the 1960""s. Now analysts say that natural gas, lighter still in carbon, may be entering its heyday, and that the day of hydrogenxe2x80x94providing a fuel with no carbon at allxe2x80x94may at last be about to dawn. As a result, experts estimate the world""s economy today burns less than two-thirds as much carbon per unit of energy produced as it did in 1860.
In the U.S., it is estimated, that the trend toward lower-carbon fuels combined with greater energy efficiency has, since 1950, reduced by about half the amount of carbon spewed out for each unit of economic production. Thus, the decarbonization of the energy system is the single most important fact to emerge from the last 20 years of analysis of the system. It had been predicted that this evolution will produce a carbon-free energy system by the end of the 21st century. The present invention shortens that period to a matter of years. In the near term, hydrogen will be used in fuel cells for cars, trucks and industrial plants, just as it already provides power for orbiting spacecraft. But ultimately, hydrogen will also provide a general carbon-free fuel to cover all fuel needs.
As noted in recent newspaper articles, large industries, especially in America, have long been suspicious of claims that the globe is warming and have vociferously negated the science of climate change. Electric utilities have even tried to stoke fears among ordinary folk that international treaties on climate change would cut economic growth and cost jobs. Therefore, it is very encouraging that some of the world""s biggest companies, such as Royal Dutch/Shell and BP Amoco, two large European oil firms, now state plainly what was once considered heresy: global warming is real and merits immediate action. A number of American utilities vow to find ways to reduce the harm done to the atmosphere by their power plants. DuPont, the world""s biggest chemicals firm, even declared that it would voluntarily reduce its emissions of greenhouse gases to 35% of their level in 1990 within a decade. The automotive industry, which is a substantial contributor to emissions of greenhouse gases and other pollutants (despite its vehicular specific reductions in emissions), has now realized that change is necessary as evidenced by their electric and hybrid vehicles.
Hydrogen is the xe2x80x9cultimate fuel.xe2x80x9d In fact, it is considered by most to be xe2x80x9cTHExe2x80x9d fuel for the next millennium, and, it is inexhaustible. Hydrogen is the most plentiful element in the universe (over 95%) and was the first element created by the xe2x80x9cBig-Bang.xe2x80x9d Hydrogen can provide an inexhaustible, clean source of energy for our planet which can be produced by various processes which split water into hydrogen and oxygen. The hydrogen can be stored and transported in solid state form. The instant patent application makes it possible to create a complete generation/storage/transportation/delivery system for such a hydrogen based economy. For example, economical, lightweight, triple-junction amorphous silicon solar cells (an invention pioneered by Stanford R. Ovshinsky, one of the instant inventors) such as those set forth in U.S. Pat. No. 4,678,679, (the disclosure of which is herein incorporated by reference) can be readily disposed adjacent a body of water, where their inherently high open circuit voltage can be used to dissociate water into its constituent gases, and collect the hydrogen so produced. Also, by placing these high efficiency solar panels on nearby farms, in water, or on land. Electricity can be generated to transport and pump the hydrogen into metal hydride storage beds that include the inventive metal hydride alloys disclosed herein. The ultra-high capacities of these alloys allow this hydrogen to be stored in solid form for transport by barge, tanker, train or truck in safe, economical form for ultimate use. Energy is the basic necessity of life and civilization for any society today and the use of hydrogen in the manner described herein as the basic source of energy would end wars fought for control of fossil fuels. Instead of xe2x80x9cfrom well to wheel,xe2x80x9d the phrase now recited will be xe2x80x9cfrom source to wheel.xe2x80x9d
In the past considerable attention has been given to the use of hydrogen as a fuel or fuel supplement. While the world""s oil reserves are depletable, the supply of hydrogen remains virtually unlimited. Hydrogen can be produced from coal, natural gas and other hydrocarbons, or formed by the electrolysis of water, preferably via energy from the sun which is composed mainly of hydrogen and can itself be thought of as a giant hydrogen xe2x80x9cfurnacexe2x80x9d. Moreover hydrogen can be produced without the use of fossil fuels, such as by the electrolysis of water using nuclear or solar energy, or any other form of economical energy (e.g. wind, waves, geothermal, etc.). Furthermore, hydrogen, although presently more expensive than petroleum, is an inherently low cost fuel. Hydrogen has the highest density of energy per unit weight of any chemical fuel and is essentially non-polluting since the main by-product of xe2x80x9cburningxe2x80x9d hydrogen is water. Thus, hydrogen can be a means of solving many of the world""s energy related problems, such as climate change, pollution, strategic dependency on oil, etc., as well as providing a means of helping developing nations.
While hydrogen has wide potential application as a fuel, a major drawback in its utilization, especially in mobile uses such as the powering of vehicles, has been the lack of acceptable lightweight hydrogen storage medium. Conventionally, hydrogen has been stored in pressure-resistant vessels under a high pressure or stored as a cryogenic liquid, being cooled to an extremely low temperature. Storage of hydrogen as a compressed gas or liquid involves the use of large and heavy vessels, making the use of hydrogen to power vehicles less feasible.
Alternatively, certain metals and alloys have been known to permit reversible storage and release of hydrogen. In this regard, they have been considered as a superior hydrogen-storage material, due to their high hydrogen-storage efficiency. Storage of hydrogen as a solid hydride can provide a greater volumetric storage density than storage as a compressed gas or a liquid in pressure tanks. Also, hydrogen storage in a solid hydride presents fewer safety problems than those caused by hydrogen stored in containers as a gas or a liquid. These alloys are fully described in U.S. Pat. No. 6,193,919, entitled xe2x80x9cHigh Storage Capacity Alloys Enabling a Hydrogen-based Ecosystemxe2x80x9d, which is hereby incorporated by reference.
With these developments in the storage of hydrogen, hydrogen now has a viable use as a fuel to power vehicles. Solid-phase metal or alloy system can store large amounts of hydrogen by absorbing hydrogen with a high density and by forming a metal hydride under a specific temperature/pressure or electrochemical conditions, and hydrogen can be readily released by changing these conditions.
With hydrogen now being a viable source to power vehicles, considerable research has been performed on designing engines to run on hydrogen rather than fossil fuels. In these designs, a hydrogen mixture is combusted inside an internal combustion engine much like gasoline and other hydrocarbons are combusted in present day internal combustion engines. With hydrogen, however, catalytic converters are not needed to treat the hydrocarbons and carbon monoxide present in the exhaust to comply with emission standards.
Internal combustion engines using gasoline or other hydrocarbon fuels typically rely on catalyst and exhaust composition sensors to comply with emission standards. It is not practical in those engines to reduce or eliminate fuel flow to one or more cylinders without also reducing or eliminating airflow in proportion (i.e. a uniform air fuel ratio must be maintained in all cylinders for exhaust composition sensors and catalysts to function effectively). The presence of air in the exhaust makes those devices less effective. Hydrogen internal combustion engines do not require exhaust hydrocarbon or carbon monoxide catalysts, so they can continue to operate cleanly when the fuel input to one or more cylinders is reduced or eliminated. In the present invention, fuel cutoff to specific cylinders is utilized to reduce engine power during periods of low power demand such as idling or when engine is under light load.
As an alternative to vehicles powered solely by internal combustion engines, hybrid-electric vehicles (HEVs) have gained popularity as having the technical capability to meet the goal of tripling auto fuel economy in the next decade. Hybrid vehicles utilize the combination of an internal combustion engine and an electric motor driven from a battery and have been proposed in a variety of configurations.
Hybrid systems have been divided into two broad categories, namely series and parallel systems. In a typical series system, an electric propulsion motor is used to drive the vehicle and the engine is used to recharge the battery. In a parallel system, both the combustion engine and the electric motor are used to drive the vehicle and can operate in parallel for this purpose.
There are further variations within these two broad categories. For example, there are systems which employ a combination of the series and parallel systems. In the so-called xe2x80x9cdual modexe2x80x9d system, the propulsion mode can be selected, either by the operator or by a computer system, as either an xe2x80x9call electricxe2x80x9d or xe2x80x9call enginexe2x80x9d mode of propulsion. In the xe2x80x9crange extenderxe2x80x9d system, a primarily electric system is used for propulsion and the engine is used for peak loads and/or for recharging the battery. In the xe2x80x9cpower assistxe2x80x9d system, peak loads are handled by the battery driven electric motor.
A further division is made between systems which are xe2x80x9ccharge depletingxe2x80x9d in the one case and xe2x80x9ccharge sustainingxe2x80x9d in another case. In the charge depleting system, the battery charge is gradually depleted during use of the system and the battery thus has to be recharged periodically from an external power source, such as by means of connection to public utility power. In the charge sustaining system, the battery is recharged during use in the vehicle, through regenerative braking and also by means of electric power supplied from a generator driven by the engine so that the charge of the battery is maintained during operation.
There are many different types of systems that fall within the categories of xe2x80x9ccharge depletingxe2x80x9d and xe2x80x9ccharge sustainingxe2x80x9d and there are thus a number of variations within the foregoing examples which have been simplified for purposes of a general explanation of the different types. However, it is to be noted in general that systems which are of the xe2x80x9ccharge depletingxe2x80x9d type typically require a battery which has a higher charge capacity (and thus a higher specific energy) than those which are of the xe2x80x9ccharge sustainingxe2x80x9d type if a commercially acceptable driving range (miles between recharge) is to be attained in operation. Further and more specific discussion of the various types of HEV systems, including xe2x80x9cseriesxe2x80x9d, xe2x80x9cparallelxe2x80x9d and xe2x80x9cdual modexe2x80x9d types, and of the present invention embodied in such systems will be presented below.
In the present application, the terms xe2x80x9chydrogen powered internal combustion enginexe2x80x9d, xe2x80x9ccombustion enginexe2x80x9d, xe2x80x9cenginexe2x80x9d, and xe2x80x9cHP-ICExe2x80x9d are used to refer to engines utilizing hydrogen fuel.
The use of hybrid drive systems offers critical advantages for both fuel economy and ultra-low emissions. Combustion engines achieve maximum efficiency and minimal emissions when operated at or near the design point speed and load conditions. Small electric motors are capable of providing very high peak torque and power. Thus, the ability to use a small combustion engine operating at maximum efficiency coupled with an electric motor operating at maximum efficiency offers an outstanding combination for minimizing emissions, providing excellent fuel economy, and maximizing acceleration.
A key enabling technology for HEVs is an energy storage system capable of providing very high pulse power a combined with high energy density while at the same time accepting high regenerative braking currents at very high efficiency. In addition, the duty cycle of a peak power application requires exceptional cycle life at low depths of discharge, particularly in charge depleting systems.
It is important to understand the different requirements for this energy storage system compared to those for a pure electric vehicle. Range is the critical factor for a practical EV, making energy density the critical evaluation parameter. Power and cycle life are certainly important, but they become secondary to energy density for an EV. A lightweight, compact, high-capacity battery is the target for pure EV applications.
An example of such a battery is the Ovonic Nickel Metal Hydride (NiMH) battery. The Ovonic Nickel Metal Hydride (NiMH) battery has reached an advanced stage of development for EVs. Ovonic electric vehicle batteries are capable of propelling an electric vehicle to over 370 miles (due to a specific energy of about 90 Wh/Kg), long cycle life (over 1000 cycles at 80% DOD), abuse tolerance, and rapid recharge capability (up to 60% in 15 minutes). Additionally, the Ovonic battery has demonstrated higher power density when evaluated for use as an EV stored energy source.
The present invention describes a hybrid vehicle having an innovative design for a hydrogen internal combustion engine. Unlike previous hydrogen internal combustion engines, the present invention does not use a throttle and utilizes a cylinder deactivation strategy during light load and idling conditions. The disclosed hydrogen powered internal combustion engine in conjunction with high powered Nickel Metal Hydride batteries provides a clean alternative to powering vehicles, bringing the world one step closer to a xe2x80x9cHydrogen Based Ecosystemxe2x80x9d.
The present invention discloses a hybrid vehicle including a hydrogen powered internal combustion engine, an electric motor for supplementing the hydrogen powered internal combustion engine, a source of hydrogen, a hydrogen fuel control system, and a rechargeable battery which is optionally a high powered rechargeable battery. The hydrogen internal combustion engine is designed to operate without a throttle. A continuous stream of air is delivered to the engine and divided into a plurality of smaller air streams each leading to a cylinder inside the engine. Prior to reaching the cylinders, a calculated amount of hydrogen is injected into each of the smaller air streams. The engine is operated at lean conditions to minimize NOx generation.
The amount of hydrogen injected into each air stream is calculated by a control system responsive to the position of the accelerator pedal and the speed of the engine. The control system incorporates an accelerator pedal position transducer to sense power requirement in response to an input from the vehicle operator.
The hydrogen internal combustion engine operates in a normal operation mode and a cylinder deactivation mode. During idling or light load conditions the hydrogen internal combustion engine operates in a cylinder deactivation mode. While in cylinder deactivation mode, one or more of the hydrogen fuel injectors cease injecting fuel into the air streams. While the hydrogen may no longer be injected into the air streams, the continuous stream of air remains unchanged and continues to flow through the engine.
An electric motor is used to supplement the hydrogen powered internal combustion engine. The electric motor is powered by a high energy density rechargeable battery. The battery may be recharged during operation of the hydrogen powered internal combustion engine. The battery system is modified to help compensate for the loss in power realized by fueling the internal combustion engine with hydrogen instead of hydrocarbon based fuels.